<!DOCTYPE html>
<html lang="en">
<head>
    <meta charset="UTF-8">
    <meta name="viewport" content="width=device-width, initial-scale=1.0">
    <title>进阶练习</title>
    <style>
        .box1{
            height: 800px;
            width: 800px;
            border: 1px solid #000;
            margin: 100px auto;
            background: url(https://img2.baidu.com/it/u=1580032289,499658214&fm=253&fmt=auto&app=120&f=JPEG?w=500&h=500), url(https://img0.baidu.com/it/u=1210860930,2344973271&fm=253&fmt=auto&app=120&f=JPEG?w=500&h=500);
            background-position: center;
            background-repeat: no-repeat;
            background-size: cover;
        }
        .box2{
            height: 200px;
            width: 200px;
            background-image:  linear-gradient(to right, blue, red);
        }
        .box3{
            margin: 0 auto;
            height: 400px;
            width: 400px;
            border: 1px solid red;
            background: url(https://img2.baidu.com/it/u=1933694560,1851305891&fm=253&fmt=auto&app=120&f=JPEG?w=500&h=500);
            background-size: cover;
            clip-path: circle(100px at 250px 250px);
        }
        .box3:hover{
            clip-path: circle(200px at 250px 250px);
        }
        .box4{
            background-image: url(https://img1.baidu.com/it/u=537284430,2902839212&fm=253&fmt=auto&app=138&f=JPEG?w=400&h=488);
            background-position: center;
            background-repeat: no-repeat;
            background-size: contain;
            height: 400px;
            width: 400px;
        }
        .box5{
            background-image: url(https://img2.baidu.com/it/u=3036593543,1861278559&fm=253&fmt=auto&app=138&f=JPEG?w=500&h=889);
            background-repeat: no-repeat;
            background-size: cover;
            position: fixed;
            bottom: 0;
            width: 100%;
            height: 300px;
        }
    </style>
</head>
<body>
    <div class="box1"></div>
    <div class="box2"></div>
    <div class="box3"></div>
    <div class="box4"></div>
    <div class="box5"></div>
</body>
</html>